2. Geomagnetism and Paleomagnetism
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Paleomagnetism and U-Pb Geochronology of the Late Cretaceous Chisulryoung Volcanic Formation, Korea
Jeong et al. Earth, Planets and Space (2015) 67:66 DOI 10.1186/s40623-015-0242-y FULL PAPER Open Access Paleomagnetism and U-Pb geochronology of the late Cretaceous Chisulryoung Volcanic Formation, Korea: tectonic evolution of the Korean Peninsula Doohee Jeong1, Yongjae Yu1*, Seong-Jae Doh2, Dongwoo Suk3 and Jeongmin Kim4 Abstract Late Cretaceous Chisulryoung Volcanic Formation (CVF) in southeastern Korea contains four ash-flow ignimbrite units (A1, A2, A3, and A4) and three intervening volcano-sedimentary layers (S1, S2, and S3). Reliable U-Pb ages obtained for zircons from the base and top of the CVF were 72.8 ± 1.7 Ma and 67.7 ± 2.1 Ma, respectively. Paleomagnetic analysis on pyroclastic units yielded mean magnetic directions and virtual geomagnetic poles (VGPs) as D/I = 19.1°/49.2° (α95 =4.2°,k = 76.5) and VGP = 73.1°N/232.1°E (A95 =3.7°,N =3)forA1,D/I = 24.9°/52.9° (α95 =5.9°,k =61.7)and VGP = 69.4°N/217.3°E (A95 =5.6°,N=11) for A3, and D/I = 10.9°/50.1° (α95 =5.6°,k = 38.6) and VGP = 79.8°N/ 242.4°E (A95 =5.0°,N = 18) for A4. Our best estimates of the paleopoles for A1, A3, and A4 are in remarkable agreement with the reference apparent polar wander path of China in late Cretaceous to early Paleogene, confirming that Korea has been rigidly attached to China (by implication to Eurasia) at least since the Cretaceous. The compiled paleomagnetic data of the Korean Peninsula suggest that the mode of clockwise rotations weakened since the mid-Jurassic. -
2. Geomagnetism and Paleomagnetism
2. GEOMAGNETISM AND PALEOMAGNETISM https://physicalgeology.pressbooks.com/chapter/4-3-geological-renaissance-of-the-mid-20th-century/ Click for audio Topic 2a 1 Topic 2a 2 q Q ELECTRIC FIELD q -Q Topic 2a 3 MAGNETIC DIPOLE Although magnetic fields have a similar form to electric fields, they differ because there are no single magnetic "charges," known as magnetic poles. Hence the fundamental entity is the magnetic dipole arising from an electric current I circulating in a conducting loop, such as a wire, with area A . The field is described as resulting from a magnetic dipole characterized by a dipole moment m Magnetic dipoles can arise from electric currents - which are moving electric charges - on scales ranging from wire loops to the hot fluid moving in the core that generates the earth’s magnetic field. They also arise at the atomic level, where they are intrinsic properties of charged particles like protons and electrons. As a result, rocks can be magnetized, much like familiar bar magnets. Although the magnetism of a bar magnet arises from the electrons within it, it can be viewed as a magnetic dipole, with north and south magnetic poles at opposite ends. Topic 2a 4 Magnetic field B Units of B Tesla (T) = kg/s 2 -A A = Ampere (unit of current) Gauss (G) = 10-4 Tesla Gamma (! )= 10-9 Tesla = 1 nanoTesla (nT) Earth’s field is about 50 "T = 50 x 10-6 Tesla Topic 2a 5 We visualize the magnetic field of a dipole in terms of magnetic field lines pointing outward from the north pole of a bar magnet and in toward the south. -
Dating Techniques.Pdf
Dating Techniques Dating techniques in the Quaternary time range fall into three broad categories: • Methods that provide age estimates. • Methods that establish age-equivalence. • Relative age methods. 1 Dating Techniques Age Estimates: Radiometric dating techniques Are methods based in the radioactive properties of certain unstable chemical elements, from which atomic particles are emitted in order to achieve a more stable atomic form. 2 Dating Techniques Age Estimates: Radiometric dating techniques Application of the principle of radioactivity to geological dating requires that certain fundamental conditions be met. If an event is associated with the incorporation of a radioactive nuclide, then providing: (a) that none of the daughter nuclides are present in the initial stages and, (b) that none of the daughter nuclides are added to or lost from the materials to be dated, then the estimates of the age of that event can be obtained if the ration between parent and daughter nuclides can be established, and if the decay rate is known. 3 Dating Techniques Age Estimates: Radiometric dating techniques - Uranium-series dating 238Uranium, 235Uranium and 232Thorium all decay to stable lead isotopes through complex decay series of intermediate nuclides with widely differing half- lives. 4 Dating Techniques Age Estimates: Radiometric dating techniques - Uranium-series dating • Bone • Speleothems • Lacustrine deposits • Peat • Coral 5 Dating Techniques Age Estimates: Radiometric dating techniques - Thermoluminescence (TL) Electrons can be freed by heating and emit a characteristic emission of light which is proportional to the number of electrons trapped within the crystal lattice. Termed thermoluminescence. 6 Dating Techniques Age Estimates: Radiometric dating techniques - Thermoluminescence (TL) Applications: • archeological sample, especially pottery. -
The Flux Line News of the Geomagnetism, Paleomagnetism and Electromagnetism Section of AGU
The Flux Line News of the Geomagnetism, Paleomagnetism and Electromagnetism Section of AGU November 2018 Fall 2018 AGU Meeting Events! The GPE Section will have primary responsibility for 10 oral, 11 poster sessions, 1 eLightning session and 1 Union session at the 2018 Fall AGU meeting, December 10-14, in addition to secondary sessions. GPE sessions cover all five conference days kicking off on Monday morning right through Friday morning (see synopsis on page 9). Many thanks go out to all our session conveners. A special thanks goes out to France Lagroix, GPE Secretary, who put together the GPE sessions for all of us. France points out that we need many OSPA judges for our student presentations. Please sign up to help us judge student presentations: (http://ospa.agu.org/ospa/judges/) Mark your calendars for these special events: • GPE Student Reception: Monday, Dec. 10, 6:00 – 7:30-8 pm, at Marriott-Marquis Hotel This is a GPE-sponsored event to help students and postdocs get to know each other and meet the GPE leadership. If you plan on attending please email Shelby Jones-Cervantes • AGU Icebreaker: Monday, Dec. 11, 6-8 pm, Convention Center, Exhibit Hall D-E • AGU Student Breakfast: Tuesday, Dec. 12 at 7 am, Marriot-Marquis Hotel First come, first served. Look for the GPE table. • Bullard Lecture: Tuesday, Dec 12 Hunting the Magnetic Field presented by Lisa Tauxe, Marquis 6. See story page 4 • GPE Business Meeting and Reception: Tuesday, Dec 11, 6:30 – 8:00 pm, Grand Hyatt Washington Hotel, Constitution Level, Room A • AGU Honors Ceremony: Wednesday, Dec. -
Paleomagnetism and Counterclockwise Tectonic Rotation of the Upper Oligocene Sooke Formation, Southern Vancouver Island, British Columbia
499 Paleomagnetism and counterclockwise tectonic rotation of the Upper Oligocene Sooke Formation, southern Vancouver Island, British Columbia Donald R. Prothero, Elizabeth Draus, Thomas C. Cockburn, and Elizabeth A. Nesbitt Abstract: The age of the Sooke Formation on the southern coast of Vancouver Island, British Columbia, Canada, has long been controversial. Prior paleomagnetic studies have produced a puzzling counterclockwise tectonic rotation on the underlying Eocene volcanic basement rocks, and no conclusive results on the Sooke Formation itself. We took 21 samples in four sites in the fossiliferous portion of the Sooke Formation west of Sooke Bay from the mouth of Muir Creek to the mouth of Sandcut Creek. After both alternating field (AF) and thermal demagnetization, the Sooke Formation produces a single-component remanence, held largely in magnetite, which is entirely reversed and rotated counterclockwise by 358 ± 128. This is consistent with earlier results and shows that the rotation is real and not due to tectonic tilting, since the Sooke Formation in this region has almost no dip. This rotational signature is also consistent with counterclockwise rota- tions obtained from the northeast tip of the Olympic Peninsula in the Port Townsend volcanics and the Eocene–Oligocene sediments of the Quimper Peninsula. The reversed magnetozone of the Sooke sections sampled is best correlated with Chron C6Cr (24.1–24.8 Ma) or latest Oligocene in age, based on the most recent work on the Liracassis apta Zone mol- luscan fauna, and also a number of unique marine mammals found in the same reversed magnetozone in Washington and Oregon. Re´sume´ : L’aˆge de la Formation de Sooke sur la coˆte sud de l’ıˆle de Vancouver, Colombie-Britannique, Canada, a long- temps e´te´ controverse´. -
5 Geomagnetism and Paleomagnetism
5 Geomagnetism and paleomagnetism It is not known when the directive power of the magnet 5.1 HISTORICAL INTRODUCTION - its ability to align consistently north-south - was first recognized. Early in the Han dynasty, between 300 and 5.1.1 The discovery of magnetism 200 BC, the Chinese fashioned a rudimentary compass Mankind's interest in magnetism began as a fascination out of lodestone. It consisted of a spoon-shaped object, with the curious attractive properties of the mineral lode whose bowl balanced and could rotate on a flat polished stone, a naturally occurring form of magnetite. Called surface. This compass may have been used in the search loadstone in early usage, the name derives from the old for gems and in the selection of sites for houses. Before English word load, meaning "way" or "course"; the load 1000 AD the Chinese had developed suspended and stone was literally a stone which showed a traveller the pivoted-needle compasses. Their directive power led to the way. use of compasses for navigation long before the origin of The earliest observations of magnetism were made the aligning forces was understood. As late as the twelfth before accurate records of discoveries were kept, so that century, it was supposed in Europe that the alignment of it is impossible to be sure of historical precedents. the compass arose from its attempt to follow the pole star. Nevertheless, Greek philosophers wrote about lodestone It was later shown that the compass alignment was pro around 800 BC and its properties were known to the duced by a property of the Earth itself. -
Paleomagnetic Stability
Paleomagnetism: Chapter 5 81 PALEOMAGNETIC STABILITY With the background information gained to this point, you appreciate the importance of isolating the charac- teristic NRM by selective removal of the secondary NRM. Theory and application of paleomagnetic stability tests are introduced here. Partial demagnetization experiments are performed in the laboratory to isolate the ChRM. Although sometimes mistaken as “magic,” these laboratory procedures are well grounded in rock magnetism theory. Field tests of paleomagnetic stability can sometimes provide crucial information about the age of a ChRM, and this question is often at the heart of paleomagnetic investigations. Lack of background in paleomagnetic stability tests often prevents interested earth scientists from understanding paleomagnetism. The material in this chapter should largely remove this obstacle. If not a “Big Enchilada,” this chapter certainly qualifies as a “Burro Grande.” PARTIAL DEMAGNETIZATION TECHNIQUES Theory and application of alternating-field and thermal demagnetization are introduced in this section. Al- though a central part of paleomagnetic investigations for some time, analysis of partial demagnetization data has become more sophisticated because of widespread availability of microcomputer systems for data analysis. Understanding modern paleomagnetism requires some familiarity with the analytical techniques that are used to decipher potentially complex, multicomponent NRM. To put the theory and techniques into practice, this section concludes with some practical examples. Theory of alternating-field demagnetization The fundamental AF demagnetization procedure is to expose a specimen to an alternating magnetic field. The waveform of the alternating magnetic field is a sinusoid with linear decrease in magnitude with time. Maximum value of this AF demagnetizing field can be labeled HAF and the waveform is schematically represented in Figure 5.1a. -
Xuan Et Al QSR 2012
Quaternary Science Reviews 32 (2012) 48e63 Contents lists available at SciVerse ScienceDirect Quaternary Science Reviews journal homepage: www.elsevier.com/locate/quascirev Paleomagnetism of Quaternary sediments from Lomonosov Ridge and Yermak Plateau: implications for age models in the Arctic Ocean Chuang Xuan a,*, James E.T. Channell a, Leonid Polyak b, Dennis A. Darby c a Department of Geological Sciences, University of Florida, 241 Williamson Hall, P.O. Box 112120, Gainesville, FL 32611, USA b Byrd Polar Research Center, Ohio State University, Columbus, OH 43210, USA c Department of Ocean, Earth, and Atmospheric Sciences, Old Dominion University, Norfolk, VA 23529, USA article info abstract Article history: Inclination patterns of natural remanent magnetization (NRM) in Quaternary sediment cores from the Received 2 February 2011 Arctic Ocean have been widely used for stratigraphic correlation and the construction of age models, Received in revised form however, shallow and negative NRM inclinations in sediments deposited during the Brunhes Chron in 15 November 2011 the Arctic Ocean appear to have a partly diagenetic origin. Rock magnetic and mineralogical studies Accepted 17 November 2011 demonstrate the presence of titanomagnetite and titanomaghemite. Thermal demagnetization of the Available online 10 December 2011 NRM indicates that shallow and negative inclination components are largely “unblocked” below w300 C, consistent with a titanomaghemite remanence carrier. Following earlier studies on the Men- Keywords: e Lomonosov Ridge deleev Alpha Ridge, shallow and negative NRM inclination intervals in cores from the Lomonosov Ridge Yermak Plateau and Yermak Plateau are attributed to partial self-reversed chemical remanent magnetization (CRM) Magnetic excursions carried by titanomaghemite formed during seafloor oxidation of host (detrital) titanomagnetite grains. -
Dennis V. Kent
Dennis Kent cv December 2020 p. 1 DENNIS V. KENT Paleomagnetics Laboratory Lamont-Doherty Earth Observatory of Columbia University Palisades, NY 10964-8000 USA [email protected] EDUCATION 1974 Ph.D. (Marine Geology & Geophysics) Columbia University, NY 1968 B.S. (Geology) City College of New York, NY APPOINTMENTS 2020– Board of Governor Professor Emeritus, Rutgers University 2007–2020 Board of Governor Professor, Rutgers University 2003 Gastprofessor, Institüt für Geophysik, ETH, Zürich (also in 1982 and 1987) 2003 Visiting Scholar, Scripps Institution of Oceanography, UCSD, La Jolla, CA 1998–2007 Distinguished Professor, Department of Earth & Planetary Sciences, Rutgers University 1998– Adjunct Senior Research Scientist, Lamont-Doherty Earth Observatory 1993 Director of Research, Lamont-Doherty Earth Observatory 1989–90 Interim Director, Lamont-Doherty Earth Observatory 1987–89 Associate Director for Oceans & Climate, Lamont-Doherty Earth Observatory 1987–98 Adjunct Professor, Dept. of Earth & Environmental Sciences, Columbia University 1984–99 Doherty Senior Scientist, Lamont-Doherty Earth Observatory 1981–87 Adjunct Associate Professor, Dept. of Geological Sciences, Columbia University 1979–84 Senior Research Scientist, Lamont-Doherty Earth Observatory 1974–79 Research Associate, Lamont-Doherty Earth Observatory, Columbia University PRINCIPAL RESEARCH INTERESTS Paleomagnetism, geomagnetism, rock magnetism and their application to geologic problems. Current interests include astrochronometric polarity time scales; paleogeography, paleoclimatology and the long-term carbon cycle; paleointensity; magnetic properties of sediments and polar ice. HONORS Fellow of the American Academy of Arts and Sciences (2012) Arduino Lecture, University of Padova (2010) William Gilbert Award, American Geophysical Union (2009) Petrus Peregrinus Medal, European Geosciences Union (2006) Docteur honoris causa, Sorbonne, Universities of Paris-IPGP (2005) Member of the U.S. -
TCSS Earth Systems Unit 3 – Earth History Information
TCSS Earth Systems Unit 3 – Earth History Information Georgia Performance Standards: SES4. Students will understand how rock relationships and fossils are used to reconstruct the Earth’s past. a. Describe and apply principles of relative age (superposition, original horizontality, cross-cutting relations, and original lateral continuity) and describe how unconformities form. b. Interpret the geologic history of a succession of rocks and unconformities. c. Apply the principle of uniformitarianism to relate sedimentary rock associations and their fossils to the environments in which the rocks were deposited. d. Explain how sedimentary rock units are correlated within and across regions by a variety of methods (e.g., geologic map relationships, the principle of fossil succession, radiometric dating, and paleomagnetism). e. Use geologic maps and stratigraphic relationships to interpret major events in Earth history (e.g., mass extinction, major climatic change, tectonic events). SES6. Students will explain how life on Earth responds to and shapes Earth systems. d. Describe how fossils provide a record of shared ancestry, evolution, and extinction that is best explained by the mechanism of natural selection. e. Identify the evolutionary innovations that most profoundly shaped Earth systems: photosynthetic prokaryotes and the atmosphere; multicellular animals and marine environments; land plants and terrestrial environments. Purpose/Goal(s): Students will understand how rock relationships and fossils are used to reconstruct the Earth’s past. -
Using Paleomagnetism, Geochronology and Numerical Methods to Create and Assess Spatiotemporal Geological Relationships Through Earth History
SPACE AND TIME: USING PALEOMAGNETISM, GEOCHRONOLOGY AND NUMERICAL METHODS TO CREATE AND ASSESS SPATIOTEMPORAL GEOLOGICAL RELATIONSHIPS THROUGH EARTH HISTORY By ANTHONY FRANCIS PIVARUNAS A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2019 © 2019 Anthony Francis Pivarunas To my family, for supporting my unique co-obsession with magnets and rocks, Scott, for opening the door, and Joe, for guiding me through it ACKNOWLEDGMENTS I thank my parents, for supporting me the entire time. Your encouragement, advice, and love are amazing. My siblings, for talking, listening, and loving. My extended family, for asking me “What is the actual use of what you’re doing, Anthony?” enough times that I finally could answer it. I need to thank the SUNY Geneseo Geology department, in particular all the amazing teachers. Scott, Dori, Nick, Amy, Jeff, Ben, and Nancy, you helped guide me into geology. Particular thanks and blame for turning me onto paleomagnetism goes to Scott. It’s all your fault. To the Geowizards, there is no one I’d rather confound the Geneseo Physics department with. The long jaunt south was all started by Rob Van der Voo, my academic grandfather, who took the time to reply to my fumbling email and get me in touch with Florida. Thank you, Rob. I want to thank the entire University of Florida Geological Sciences department. Special thanks to the unsung heroes in the office and workshops: Pam, Carrie, Kristin, Diana and Dow and Ray. Thanks to all my committee members: Dave (for teaching me how to be a careful scientist), Alessandro (for teaching me how to be a creative scientist), Ray (for teaching me how to be a useful scientist), and Jim (for teaching me to be a communicative scientist). -
Paleomagnetism, Magnetic Anisotropy and U-Pb Baddeleyite
Precambrian Research 317 (2018) 14–32 Contents lists available at ScienceDirect Precambrian Research journal homepage: www.elsevier.com/locate/precamres Paleomagnetism, magnetic anisotropy and U-Pb baddeleyite geochronology of the early Neoproterozoic Blekinge-Dalarna dolerite dykes, Sweden T ⁎ Zheng Gonga, , David A.D. Evansa, Sten-Åke Elmingb, Ulf Söderlundc,d, Johanna M. Salminene a Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, CT 06511, USA b Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87 Luleå, Sweden c Department of Geology, Lund University, SE-223 62 Lund, Sweden d Swedish Museum of Natural History, Laboratory of Isotope Geology, SE-104 05 Stockholm, Sweden e Department of Geosciences and Geography, University of Helsinki, Helsinki 00014, Finland ARTICLE INFO ABSTRACT Keywords: Paleogeographic proximity of Baltica and Laurentia in the supercontinent Rodinia has been widely accepted. Blekinge-Dalarna dolerite (BDD) dykes However, robust paleomagnetic poles are still scarce, hampering quantitative tests of proposed relative positions Sveconorwegian loop of the two cratons. A recent paleomagnetic study of the early Neoproterozoic Blekinge-Dalarna dolerite (BDD) Baltica dykes in Sweden provided a 946–935 Ma key pole for Baltica, but earlier studies on other BDD dykes discerned Paleomagnetism large variances in paleomagnetic directions that appeared to indicate more complicated motion of Baltica, or Magnetic anisotropy alternatively, unusual geodynamo behavior in early Neoproterozoic time. We present combined paleomagnetic, U-Pb baddeleyite geochronology rock magnetic, magnetic fabric and geochronological studies on BDD dykes in the Dalarna region, southern Sweden. Positive baked-contact and paleosecular variation tests support the reliability of the 951–935 Ma key pole (Plat = −2.6°N, Plon = 239.6°E, A95 = 5.8°, N = 12 dykes); and the ancient magnetic field was likely a stable geocentric axial dipole at that time, based on a positive reversal test.